Electrostatic spray assembly

ABSTRACT

An electrostatic spraying assembly is provided. The spraying assembly includes a housing having a fluid inlet passage that is connectable to a fluid source and communicates with a plurality of discharge passageways each of which extends through the housing to a downstream end at a discharge end of the housing. The housing has a one piece construction and is made of an electrically insulative material. The spraying assembly also includes an electrode assembly. The electrode assembly includes a plurality of elongate electrode elements each of which is disposed in a respective one of the discharge passageways in the housing and an electrode header. The electrode header is electrically connectable to a voltage source and each of the electrode elements is electrically connectable to the electrode header.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims the benefit of U.S. Provisional PatentApplication No. 60/544,269 filed on Feb. 12, 2004.

FIELD OF THE INVENTION

The present invention relates generally to spray nozzle assemblies, andmore particularly, to electrostatic spray nozzle assemblies thatelectrostatically charge fluids discharging from spray nozzles tofacilitate liquid particle breakdown and distribution.

BACKGROUND OF THE INVENTION

Electrostatic spray nozzle assemblies are utilized for applying oil andother coating and lubricating fluids in various manufacturing processes.Electrostatic spray nozzle assemblies, such as shown in U.S. Pat. No.4,749,125, discharge a plurality of fluid flow streams which areelectrostatically charged and atomized by means of a high voltageelectrode with the assistance of a grounded induction bar fordisposition onto items to be sprayed or coated, typically as they areconveyed past the spraying apparatus.

Heretofore, such electrostatic assembly spray nozzle assemblies havesuffered from various operating and maintenance problems. For example,imprecise manufacture and assembly of such spray nozzles and chargingelectrodes can result in high voltage leakage that can significantlyaffect the operating efficiency of the spray operation. Fluid leakageproblems also can adversely affect the spray distribution and lead towaste of costly spray liquids.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide an electrostaticspray nozzle assembly that is adapted for more efficient and reliablespraying of oils and other lubricating and coating fluids.

Another object is to provide an electrostatic spray nozzle assemblywhich includes electrostatic charging electrodes that are adapted formore precise manufacture and mounting within the nozzle assembly, andhence more efficient operation with reduced power consumption andincreased life expectancy.

A further object is to provide an electrostatic spray nozzle assembly ofthe foregoing type which is operable for electrostatically charging aplurality of fluid flow streams for more uniformly coating orlubricating of items that are sprayed.

Still another object is to provide an electrostatic spray nozzleassembly of the above kind which is adapted for more effectivelyatomizing the fluid flow streams so as to produce a uniform fineparticle distribution onto items being sprayed.

Still another object is to provide an electrostatic spray nozzleassembly that can have relatively large fluid passages that resistclogging and are easy to clean.

Still another object is to provide an electrostatic spray nozzleassembly that requires a relatively low voltage at the nozzle tipthereby improving safety and reducing the tendency of sparking.

Yet another object is to provide such an electrostatic spray nozzleassembly which is relative simple in construction and lends itself toeconomical manufacture.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative spray nozzle assembly inaccordance with the invention;

FIG. 2 is a partial vertical section view of the spray nozzle assemblyshown in FIG. 1;

FIG. 3 is a perspective view of an electrode needled assembly utilizedin the illustrated electrostatic spray nozzle assembly;

FIG. 4 is a perspective view of a housing block used in the illustratedspray nozzle assembly;

FIG. 5 is a perspective view of a cover plate used in the illustratedspray nozzle assembly;

FIG. 6 is a perspective view of an alternative embodiment ofelectrostatic spray nozzle assembly in accordance with the invention.

FIG. 7 is a partial vertical section view of the spray nozzle assemblyshown in FIG. 6;

FIG. 8 is a perspective view of the spray nozzle assembly shown in FIG.6 with the cover and electrode assembly removed;

FIG. 9 is a perspective view, similar to FIG. 8, with the electrodeinserted in the housing block;

FIG. 10 is a perspective view of still a further alternative embodimentof electrostatic spray nozzle assembly in accordance with the inventionutilizing a different form of electrode assembly;

FIG. 11 is a vertical section view of the spray nozzle assembly shown inFIG. 10; and

FIG. 12 is a perspective view in partial section of an alternativeembodiment of electrostatic spray nozzle assembly which includes asingle electrode pin.

While the invention is susceptible of various modifications andalternative constructions, certain illustrated embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific forms disclosed, but on the contrary, theintention is to cover all modifications, alternative constructions andequivalents falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now more particularly to the drawings, there is shown in FIGS.1 and 2 an illustrative electrostatic spraying assembly 10 embodying thepresent invention, which is adapted for directing an elongated spray ofoil or other lubricating or coating fluid on items conveyed below thespray assembly 10. The illustrative spray nozzle assembly 10 basicallycomprises an elongated housing 11 supported in adjacent relation to afluid supply pipe 12, an electrode assembly 14 for charging fluidpassing through and directed from a lower discharge end 13 of thehousing 11, and an induction bar 15 disposed in parallel spaced relationto the discharge end of the housing 11 for enhancing liquid particlebreakdown. The housing 11 in this case is supported by the fluid supplypipe 12 by means of a plurality of transversely directed conduitsections 16 that communicate between the fluid supply pipe 12 and fluidinlet ports 16 a in a side of the housing.

In accordance with an important aspect of the invention, the electrodeassembly comprises a metallic block or header as well as a plurality ofelectrode elements in the form of pins each disposed within a respectivefluid passageway communicating with the fluid inlet ports of the housingfor charging fluid as it passes along the length of the pins and isdischarged from the spray nozzle assembly. To this end, in theillustrated embodiment, the electrode 14 comprises a plurality ofelectrode pins 14 a which are disposed in a longitudinally spaced arrayfrom a common header or strip 14 b (see, e.g., FIGS. 2 and 3). Eachelectrode pin 14 a, which in this instance is generally verticallyoriented, is concentrically disposed in a respective fluid passageway 26in the housing 11 (shown without the pins in FIG. 4) that is sizedlarger than the pin 14 a such that an annular fluid flow passage isdefined between the pin and the housing passage. The electrode 14 ismade of a highly conductive metal material with the electrode pins 14 apreferably being press fit within respective apertures within theelectrode header 14 b. The electrode header strip 14 b in this case isdisposed within a fluid inlet passage in the form of an elongated,longitudinal flow channel 18 of the housing 11 having a greatertransverse width than the strip 14 b (see, e.g., FIG. 2) for defining alongitudinal fluid flow passage communicating between the fluid inletports 16 a of the housing and the annular fluid passages about theelectrode pins 14 a.

For enclosing the upper end of the elongated flow channel 18, thehousing 11 has a cover 19 which is secured to the upper end of thehousing 11 by appropriate fastening bolts with a sealing gasket 21interposed there between. The header strip 14 b of each electrodeassembly 14 is retained in position within the flow channel 18 by bolts20 which extend through the cover 19, and each electrode header strip 14b is connected to a high voltage line through a conventional bananacoupling 22 (see FIG. 2).

In keeping with the invention, the electrode pins 14 a each terminatewith a gradually tapered pointed end 14 c which maximizes charging andultimate liquid particle breakdown upon discharge from the sprayassembly. While the theory of operation is not entirely understood, itis believed that the sharp points 14 c of the pins 14 a accumulate theelectrical charge pursuant to a theory known as the Gauss theorem. Theenhanced electrical charging of the fluid as it is directed along thepins 14 a and discharged past the sharp pointed ends 14 c furtheroptimizes atomization and charging the fluid particles, which by virtueof their repelling nature, are more uniformly directed onto the items tobe coated or lubricated. Hence, the pointed ends of the electrode pins14 a enhance the generation of smaller-sized fluid droplets, which isparticularly important in airless electrostatic spraying systems.

The electrode pins 14 a preferably each protrude outwardly of thedischarge end of the housing 11 a predetermined distance “x,” such asabout ¼ inch (see FIG. 2). It has unexpectedly been found that theprotruding electrode pin arrangement maximizes liquid flow rate throughthe spray nozzle assembly. Again, although the theory of operation isnot entirely understood, it is believed that the greater surface area ofpins over which the liquid travels facilitates liquid flow and dischargefrom the spray nozzle assembly. The increased contact with the electrodepins further enhances charging of the liquid and ultimate atomization.The housing 11 in this case is formed with a plurality of generallyfrustoconical exit points (see, e.g., FIGS. 2 and 7) through which theelectrode pins 14 a concentrically protrude for reducing the effect ofsurface tension on the liquid as it discharges from the housing aboutthe electrode pins.

In carrying out a further important feature of the invention, theelectrode receiving body of the housing 11 has a one-piece blockconstruction which facilitates precision concentric mounting of theelectrode pins 14 a within the housing passageways and which preventsfluid and high voltage leakage. The illustrated housing 11 includes aone-piece body 25 (see, e.g., FIG. 4) preferably machined from plasticstock, with the pin receiving flow passageways 26 being drilled in thebody and the longitudinal channel 18 being milled. It will be understoodby one skilled in art that by virtue of such one-piece housing blockconstruction, there are no parting planes associated with the liquidflow passageways 26 typical of multi-part housings, nor fasteners forretaining a multi-part housing body in assembled condition at suchparting planes. The resulting improved dimensional tolerances enhanceeven charging of the fluid as it travels along the perimeters of theelongated electrode pins 14 a. As a result of the novel electrode designand arrangement, the electric spray nozzle assembly of the presentinvention has been found to have significantly improved operatingefficiency over prior art spray devices of such type. For effectingspray performance comparable to such prior art spray devices, thesubject electrostatic spray nozzle assembly has been found to beoperable at 30 to 50 percent lower voltage requirements.

In the embodiment of FIGS. 1 and 2, it will be seen that the spraynozzle housing 11 includes three housing bodies 25 supported in alongitudinal array, each having a respective electrode assembly 14comprising a header 14 b and a plurality of pins 14 a, and a respectivecover 19. The fluid inlet port 16 a of each electrode body 25 is coupledto the fluid supply pipe 12 by a respective conduit section 16. Forpurposes of illustration, the electrode assemblies are shown in partialsection in FIG. 2 to depict the electrode pin arrangement. FIGS. 6-9disclose a similar electrostatic spray nozzle assembly, but utilizing asingle housing body 25, cover 19, and electrode assembly 14.

In carrying out a further feature of the invention, the induction bar 15is mounted for selective positioning relative to the downstream ends ofthe electrode pins 14 a for maximizing the effect of the electricalfield therebetween on the discharging liquid, and hence, maximizingliquid particle breakdown. As shown in FIG. 1, the induction bar 15, inthis case, is supported by elongated arms 30 fixed in depending angledrelation to opposite ends of the housing 11. The induction rod 15 isselectively positionable within elongated slots 31 formed in thesupporting arms 30 for effecting the desired spray characteristics.

In operation of the spray nozzle assembly 10, it will be seen that oilor other lubricating or coating fluid may be supplied through the liquidsupply pipe 15 and communicate with housing inlet ports 16 a through theconduit sections 16. The fluid entering the housing inlet ports willcommunicate through the longitudinal flow channel 18 to and through thedepending flow passageways 26 in surrounding relation along the lengthof the electrode pins 14 a, being charged along the entire length oftravel. Upon discharge from the housing 11, the pointed ends 14 c of theelectrode pins 14 a enhance charging of the discharging fluid, such thatupon entering the electrical field 23 (see FIG. 1, for example) betweenthe electrode pins 14 a and the induction bar 15, the liquid isdispersed into fine particle spray with the repelling charges of theparticles effecting substantially uniform distribution onto itemspassing below the spray nozzle assembly 10 to be coated.

While in the embodiment illustrated in FIGS. 1-9, fluid is electricallycharged by passage about the electrode pins 14 a, alternatively, asdepicted in FIGS. 10 and 11, fluid may be directed through the electrodeitself. To this end, the electrode can include a plurality of electrodetubes 32 having flow passages extending therethrough. With the FIGS. 10and 11 arrangement, fluid may be directed through the flow passages inthe electrode tubes 32 and discharged from flow openings at theirterminal ends 32 a. As the fluid passes through the electrode tubes 32,it is charged such that when the fluid exits the tubes and enters theelectrical field between the terminal ends 32 a of the tubes and theinduction bar 15, the fluid is dispersed into a fine particle spray. Theuse of the electrode tubes 32 provides relatively large flow passagesthat are more resistant to clogging and are easier to clean. Moreover,according to a further aspect of the invention, to enhance safety, theelectrode tubes 32 can be arranged such that each tube terminates asmall distance S (FIG. 11) from the electrode block or header 14 binside the longitudinal fluid inlet channel 18 of the housing. As aresult of this arrangement, the electrode tubes 32 are not in directelectrical contact with the electrode block or header. With thisarrangement, the electrode tubes 32 will not be charged at a highelectrical potential that could pose a safety hazard. Instead, theelectrode tubes are charged inductively due to their proximity to theelectrode header 14 b. The inductive charging of the electrode tubes 32will provide sufficient charging to provide the desired level of addedcharge to the fluid passing through the tubes 32. Accordingly, safety ofthe spray operation is increased without significant degradation inspray performance.

Referring now more particularly to FIG. 12 of the drawings, there isshown an alternative embodiment of the spray nozzle assembly 35 inaccordance with the invention, which utilizes a single electrode pin 36.The spray nozzle assembly 35 again includes a one-piece housing body 38,in this case having gun shape with an upstream cylindrical end portionand a downstream frustoconical end portion. The housing body 38, whichagain can be machined from plastic stock material, has longitudinalpassageway 39 which includes a relatively small diameter downstreampassageway section 39 a within which the electrode pin 36 isconcentrically mounted for defining an annular liquid flow passagesimilar to that described previously. The longitudinal passageway 39includes an enlarged diameter passageway section 39 b which communicateswith a radial inlet port 40 to which a fluid supply conduit 41 isconnected. The passageway 39 further includes an enlarged counter boresection 39 c at the upstream end of the body 38 within which a highvoltage line 42 connects with an upstream end of the electrode pin 36through a banana coupling 44. The electrode pin 36 in this case has anenlarged threaded steam portion 45 to facilitate coupling with the highvoltage supply line.

In carrying out a further feature of the invention, the electrode pin 36in this case is selectively positionable within the passageway section39 a for the desired spray and liquid flow rate to be generated by thespray nozzle assembly. To this end, a washer configured shim 48 having aselectively determined longitudinal width “w” is interposed between thehigh voltage coupling and a downstream end wall of the enlarged counterbore section 39 c for selectively locating the electrode pin 36 withinthe passageway 39 a, and hence, selectively establishing the distance“x” the electrode pin 36 extends beyond the downstream end of thehousing body 38. It will be seen that a thicker shim 48 will lead toreduced exposed needle surface at the tip of the nozzle body 38, andhence decrease the flow rate. Thinner shims 48 will enable a greaterexposed needle surface area at the tip of the nozzle body and hence,increase the flow rate. In this manner, an optimum flow rate can bereadily established through selection of desired shim width.

From the foregoing, it can be seen that the electrostatic spray nozzleassembly of the present invention is adapted for a more efficient andreliable spraying of oils and other lubricating and coating fluids. Thespray nozzle assembly includes electrostatic charging electrodes thatare adapted for more precision manufacture and mounting within thenozzle housing, and hence, more efficient operation with reduced powerconsumption and increased life expectancy. The spray nozzle assemblyfurther is effective for more effectively optimizing fluid flow streamsfor uniform fine particle distribution onto the sprayed items.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. An electrostatic spraying assembly comprising: a housing having afluid inlet passage that is connectable to a fluid source andcommunicates with a plurality of first passageways each of which extendsthrough the housing to a downstream end at a discharge end of thehousing, said housing having a one piece housing body made of anelectrically insulative material, said housing body being formed with anelongated internal channel disposed between front and rear housing wallsand end walls at opposite ends of said channel, the whole of said onepiece housing body including said front, rear and opposite end walls, acover enclosing a top end of said housing body and elongated channel;and an electrode assembly including an elongated electrode headerdisposed in said internal channel and a plurality of elongate electrodeelements each of which is supported in coaxial relation to and within arespective one of said first passageways in the housing, said internalchannel defining a flow passageway between said fluid inlet passage andsaid first passageways for directing fluid to said first passageways andinto contacting relation with said electrode elements, and saidelectrode header being electrically connectable to a voltage source forelectrically charging said electrode elements and liquid flowing incontact therewith prior to discharge of the liquid from the sprayingassembly.
 2. The electrostatic spraying assembly of claim 1 wherein theelectrode elements comprise pins each having a gradually tapered pointedend and being arranged in the respective first passageway such thatfluid can flow through the first passageway around the electrodeelement.
 3. The electrostatic spraying assembly of claim 1 wherein theelectrode elements comprise tubes each having an fluid passagewayextending therethrough that is in fluid communication with the fluidinlet passage in the housing and a terminal end through which fluid canbe discharged.
 4. The electrostatic spraying assembly of claim 1 whereineach of the electrode elements protrudes outwardly beyond the dischargeend of the housing.
 5. The electrostatic spraying assembly of claim 1wherein each of the electrode elements is attached to the electrodeheader.
 6. The electrostatic spraying assembly of claim 1 wherein eachof the electrode elements is arranged in spaced relation from and not indirect electrical contact with the electrode header such that theelectrode elements are charged inductively by the electrode header. 7.The electrostatic spraying assembly of claim 1 further including aninduction element supported adjacent to the discharge end of thehousing.
 8. The electrostatic spraying assembly of claim 7 wherein theinduction element is carried by support arms such that the position ofthe induction element relative to the discharge end of the housing canbe selectively adjusted.
 9. An electrostatic spraying assemblycomprising: a housing having a fluid inlet passage that is connectableto a fluid source and a plurality of first passageways each of whichextends though the housing to a downstream end at a discharge end of thehousing; and an electrode assembly including an electrode header and aplurality of metallic elongated hollow electrode tubes each of which isdisposed within a respective one of the first passageways in the housingsuch that each electrode tube extends though at least substantially theentire length and out a lower end of the respective first passagewaywith a first portion of the electrode tube being arranged in therespective first passageway and a second portion of the electrode tubeprotruding out of the respective first passageway with the secondportion of the electrode tube having a length relatively shorter than alength of the first portion; said electrode tubes each defining a fluidpassageway extending therethrough which is in communication with thefluid inlet passage in the housing and having a terminal end throughwhich fluid can be discharged, and said electrode header beingelectrically connectable to a voltage source for electrically chargingthe electrode tubes and fluid passing through the tubes prior todischarge from the spray assembly.
 10. The electrostatic sprayingassembly of claim 9 further including an induction element supportedadjacent to the discharge end of the housing.
 11. The electrostaticspraying assembly of claim 9 wherein the induction element is carried bysupport arms such that the position of the induction element relative tothe discharge end of the housing can be selectively adjusted.
 12. Theelectrostatic spraying assembly of claim 9 wherein the electrode headeris arranged in the fluid inlet passage.
 13. The electrostatic sprayingassembly of claim 9 in which said electrode tubes protrude a distance ofabout ¼ inch from said housing.
 14. The electrostatic spraying assemblyof claim 9 in which each of said electrode tubes is supported in spacedapart relation from and not in direct electrical contact with theelectrode header such that the electrode tubes are charged inductivelyby the electrode header.
 15. The electrostatic spraying assembly ofclaim 9 in which said electrode tubes define a constant diametercylindrical passageway from a location within said housing to adischarge end of the electrode tube from which fluid is directed fromthe spraying assembly.
 16. An electrostatic spraying assembly forspraying oils and other coating fluids comprising: a housing having afluid inlet passage that is connectable to a fluid source and aplurality of first passageways each of which extends through the housingto a downstream end at a discharge end of the housing; and an electrodeassembly including an electrode header and a plurality of metallicelongated hollow electrode tubes each of which is disposed within arespective one of the first passageways in the housing; said electrodetubes each being fixedly mounted within a respective first passagewayfor defining a constant diameter cylindrical passageway from a locationwithin said housing to a discharge end of the tube, and said electrodeheader being electrically connectable to a voltage source forelectrically charging the electrode tubes and fluid passing through thetubes prior to discharge from the spray assembly, and a single inductionrod supported in predetermined relation to a discharge end of saidelectrode tubes for singularly creating an electrical field forenhancing fluid particle breakdown of fluid discharging from theelectrode tubes, said electrode header comprising a metallic blockhaving a width greater than the diameter of the cylindrical passageway.17. An electrostatic spraying assembly comprising: a housing made of anelectrically insulative material having a fluid inlet passage that isconnectable to a fluid source and a plurality of first passageways eachof which extends through the housing to a downstream end at a dischargeend of the housing; and an electrode assembly including an electrodeheader and a plurality of metallic elongated hollow electrode tubes eachsupported by said housing in coaxial relation to and at least partiallywithin a respective one of said first passageways, said electrode-tubeseach defining a fluid passageway extending therethrough which is incommunication with the fluid inlet passage in the housing and having aterminal end from which fluid is discharged, said electrode header beingelectrically connectable to a voltage source, and said electrode tubeseach being supported in spaced apart relation from and not in directelectrical contact with the electrode header such that the electrodetubes are charged inductively by the electrode header and in turn chargefluid passing through the electrode tubes prior to discharge from saidspraying assembly.